Exothermic warhead technology has been shown to produce benefits by combining kinetic and thermal energies in the attack process (Bailey and Nooker, “Coruscative Liner Materials”, Applied Physics Lab, 1963). Later studies by Zaviatsanos and Riley (1990) further confirmed the benefits of reactive intermetallic systems as fragmenting warhead systems. Exothermic or pyrophoric materials have also been investigated for compound target effects, such as the initiation of fuels and other combustibles. However, the radial dispersion of thermal energy of conventional reactive intermetallic materials is low, and the materials are subject to shielding. For conventional penetrators to perform optimally, key characteristics include material density, fracture toughness and grain size/orientation. In some existing systems, grain size can be on the order of millimeters. This large grain structure produces orientation anomalies, e.g., from the pancake forging process, and is in part responsible for a high rejection rate of forged liner products.
Problems with conventional reactive intermetallic systems include their low density, their inability to fully react, and their lack of physical strength necessary to survive the high-vibration environments of military hardware. This is due to the fact that approaches to date have utilized pressed powders. Many of these systems have failed either in production, or through vibration testing, both of which can result in frictional initiation. As reactive powders are pressed, each powder element has trapped gas on it, typically oxides. When reacted in a highly constrained manner, the gases create very high, localized pressures, which tend to tear the pressed body apart, reducing the amount of large mass available to impart thermal damage. Furthermore, long time exposure of powder metallurgy materials in storage makes them susceptible to moisture and vibration, and their lack of inherent mechanical strength has a direct impact on the fragment size available for target interaction. In addition, pyrophoric solid metals that rapidly oxidize when explosively deformed do not meet their anticipated benefits, since burning is typically a surface phenomenon, and the bulk of these incendiary fragments are only slightly elevated in temperature.
The present invention overcomes these problems by incorporating reactive materials in multilayer structures, which have densities that approach theoretical values, and which have good structural integrity and good mechanical properties.